In a prior art rectifier circuit, for example as shown in FIG. 4 of Japanese Patent Laid-Open Application No. 59-198872 published on Nov. 10, 1984 having the title of "Rectifying Power Supply Circuit", an alternating power supply is rectified and converted to a direct current power supply, and a higher harmonic wave of the power supply current is suppressed. Such a rectifier circuit has the switching element connected to the output terminal of the rectifier circuit and obtains the synchronous setting signal by multiplying the voltage signal of the alternating power supply and the difference signal between the direct current output voltage generated at the output terminal of the rectifier circuit and the setting voltage set previously, compares the synchronous error signal and the alternating current flowing through the rectifier circuit, and switches ON and OFF the switching element corresponding to the polarity based on the difference of the compared result.
The circuit of the prior art discloses that the load connected to the direct current power supply is controlled by the step-up chopper circuit, but it does not disclose that the step-up chopper circuit is further connected to an inverter and a motor as a load. Further, in the prior art rectifier circuit which uses the step-up chopper circuit, there is such a drawback that the magnitude of the direct current input voltage applied to the inverter is not controlled to the value which is lower than the peak value of the alternating current input voltage so that the speed control region of the motor becomes narrow.